Electrolytic preparation of capillary-active quaternary ammonium hydroxides



L. BOCK Filed Dec.

Nov. 21, 1944.

ELECTROLYTIC PREPARATION 0F cAPILLARY-ACTIVE QUATERNARY AMMONIUM HYDROXIDES Patented Nov. 21, 1944 Laar-ACTIVE Hypnoxmus l Louis H. Bock, Huntln to Rhm & Haas Company, a corporation of Delaware QUATERNARY AMVIQNIUM gdon Valley, Pa., assigner Philadelphia, Pa.,

` Application December 1s, 1941, serial No. 422,838 '1 claims. (c1. 20a-7,2)

This invention relates to a process for preparing quaternary ammonium hydroxides having capillary activity. In particular this invention deals with the preparation of quaternary ammonium hydroxides from corresponding salts 'shaving an N-substituent containing vat least 10 carbon atoms.

In application Serial No.A 310,360, filed December 21, 1939, of which this application is acontinuation-in-part, there is described an electrolytic method for preparing quaternary ammonium hydroxides. This method is generally applicable to the conversion of Quaternary salts to hydroxides when the groups in the molecule are not readily reduced and the molecules have suiiiclent stability to prevent decomposition to ytertiary amines and hydrocarbons. By the use of porous refractory diaphragmsgood purity of the desired hydroxide may be attained with good yield. As one or more of the N-substituents is made large enough to give soap-like properties to the quaternary ammonium hydroxide, difliculties appear, however, in that coarse diaphragms become necessary and foam forms about the cathode. When a coarse diaphragm sets oli the cathode, anions tend to diffuse into 'thecathode compartment to decrease the purity of the product. With evolution of hydrogen about the cathode the formation of foam as 'a result of capillary activity or soap-like properties creates a problem. y

lIt is an object of this invention to prepare Quaternary ammonium hydroxides having capillary activity. It is an object to prepare longchained Quaternary hydroxides with a minimum contamination orquaternary saltsand decomposition products thereof. Itis also an object to provideV an electrochemical method vof preparing long-chained, non-aromatic quaternary ammonium hydroxldes, which is free from dimcultles heretofore encountered.

These objects are accomplished by placing an aqueous solution -of a capillary-active quaternary ammonium salt in Vthe intermediate compartment-of an electrolytic cell having an anode set of! by a refractory diaphragm of dened 'porosity to form an kanode compartment which contains an aqueous solution of a strong acid and having a cathode set off by a refractory diaphragm of deilned porosity to form a cathode compartment which contains an aqueous solution of an alkali, said diaphragms forming the said intermediate compartment, and passing a unidirectional current through said cell whereby the Ysalt-forming lnary type of compound,

anions of said salt are substantially replaced with hydroxyl ions.

The porosity of the diaphragms may be def' ned by the rate of iiow therethrough. It has been found Ithat diaphragms giving a flow between about 0.001 cc. and about 0.015 cc. of water at 420" C. per square centimeter per hour under a vhydrostatic head of 20 cm. are suitable for preparation of quaternary ammonium hydroxides by this invention. The diaphragms are composed of a refractory material such as Carborundum. Alundum, porcelain, or other ceramic composition.

A suitable multi-compartment cell is illustrated in vertical cross-section in the drawing. The anode I is surrounded by a porous diaphragm 2 to form an anode compartment la which is sealed by a cover 3 having the tube 4 through which gases may be withdrawn from the anode compartment. A short distance from diaphragm 2 is located a secondfdiaphragm 5, which sets -oif the cathode 6. forms a cathode compartment 6a, and at the same time in conjunction with diaphragm 2 forms an intermediate compartment 5a. The various parts described are assembled within a container l.

As ananode there may be used any conducting vmaterial which isrelatively inert to halogens or oxygen, such as carbon, carbon impregnated with oil or paraffin, or one of the platinum group The .cathode is composed of a metal which is not attacked by alkali, such as iron or platinum. The cathode Grand container 'l may be one andthe same unit. since an alkali-resistant metal serves satisfactorily as a container. With separate cathode and container, the latter Vmay be composed of a. material such as glass or vitreous ware.

It will be evident to those skilled in the art .that the electrolytic cell used Vmay take many shapes and dimensions. It is, of course, desirable to vkeep the cell as compact as possible to decrease internal resistance and increase efficiency.

As a'quaternary ammonium ysalt there-may be used any salt having N-substituents of suflicient .size to impart capillary activity tothe compound. lCapillary activity is generally Vfirst noted with a substituent of 10 carbon atoms and is particularly marked in the' case of'quaternary ammonium compounds having at least .one substituent of 12 to 18 rcarbon atoms. The N-substituents are preferably aliphatic or arylaliphatic, as these give stable hydroxides. substituents of Vother types tend to cause decomposition .of the quater even under the vfavorable conditions encountered in the method here disclosed. The aliphatic or arylaliphatic substituents may be straight, branched, saturated, unsaturated, or may contain cycles, excluding aromatic cycles which are attached directly to the Quaternary nitrogen atoms. The term nonaromatic" is used herein to characterize compounds in which an aryl ring is not directly oonnected to the pentavalent nitrogen. These substituents may be hydrocarbon groups or they may be groups which contain stable functional groups such as hydroxyl, ether, or amino groups. Typical substituents imparting capillary activity are decyl, dodecyl, cetyl, octadecyl, octadecenyl, dodecyloxymethyl, octadecyloxymethyl, undecenyl, undecenyloxymethyl, butylbenzyl, diisobutylbenyl, butylnaphthoxyethyl, diisobutylphenoxyethyl,

, diisobutylcresoxyethyl, diisobutylchlorophenoxyethyl, octylphenoxyethoxyethyl, etc. In addition to at least one such group which is capable of imparting capillary activity, other aliphatic or arylaliphatic groups are attached to the quaternary nitrogen atom, such as methyl, ethyl, hydroxyethyl, aminoethyl, propyl, isopropyl, butyl, capryl, ethoxyethyl. caproxymethyl, benzyl, benzyloxymethyl, etc. i

In general, suitable salts which may be converted by the herein-described process are of the formula:

wherein X is a salt-forming anion such as chloride, bromide, iodide, sulfate, acetate, phosphate, etc. and R1, Rz, Re. and R4 are aliphatic or arylaliphatic groups at least one of which contains at least 10 carbon atoms. Suitable salts are decyl diethyl benzyl ammonium' bromide, dodecyl dimethyl benzyl ammonium chloride, octadecyl trimethyl ammonium chloride, cetyloxymethyl dimethyl methylbenzyl ammonium chloride, dodecyl phenoxyethoxyethyl dimethyl ammonium chloride, or other water-soluble quaternary ammonium compound exhibiting surface activity.

In converting a salt o! the above type to the corresponding hydroxide an aqueous solution of the salt is prepared and placed in a cell between two refractory diaphragme having a porosity permitting a flow of about 0.001 cc. to about 0.015 cc. of Water at 20 C. per square centimeter per hour under a 20 cm. head. Behind one diaphragm a solution of a strong acid, such as hydrochloric acid or sulfuric acid, is placed as the anoiyte. Behind the other diaphragm a solution of an alkali, such as sodium or potassium hydroxide, or a, Quaternary ammonium hydroxide of low molecular weight, is placed to serve as the catholyte. Current is then passed through the cell. Neither voltage nor current density are critical factors in this process although it is, of course, desirable to establish and maintain conditions such that as good current efficiency as possible is obtained by keeping the voltage relatively low, four to twenty volts being suitable, and keeping the overvoltage also low by moderate to low current densities, lvalues for which may be as high as three amperes per square decimeter. During the passage of electric current the temperature of the cell rises. Temperatures up to about 50 C. are often helpful in maintaining good solubility and low viscosity of the solutions, Excessive temperatures, however, in some cases cause las chloride, chlorine is liberated at decomposition of the long-chained Quaternary compounds but decomposition can be avoided by control of voltage and amperage or by cooling. Under the influence of the current the saltforming anion migrates through the diaphragm about the anode and, in the case of such anions this pole. The Quaternary ammonium ion is apparently present in a soap-like micelle which escapes only with difficulty into the cathode compartment through a diaphragm of the range of porosity above-specified.k As a result, practically pure Quaternary ammonium hydroxide is obtained in the intermediate compartment. The process is continued until the original anion is exhausted from this compartment or reduced to any required level.

The description of the preparation of longchained Quaternary ammonium hydroxides is amplified in the following illustrative examples.

Eample 1 A solution of benzyl dimethyl octadecyl ammonium chloride in water, adjusted to a normality of 1.5, was placed in the intermediate compartment of a cell having a Carborundum cup surrounding a graphite anode and an Alundum jar separating-the intermediate compartment from the cathode compartment. An iron screen served as a cathode. The porosity of the Carborundum cup allowed the ow of 0.001 cc. of water per square centimeter per hour under a 20 cm. head. The Alundum vessel permitted a flow of 0.008 cc. of water per square centimeter per hour. A 15% solution of hydrochloric acid was placed in the anode compartment while a 10% solution of sodium hydroxide was run into the cathode compartment. A current of two amperes at seven volts was passed through the cell. There was an increase in the volume of liquor in the intermediate compartment probably due to electroendosmosis. This necessitated occasional withdrawal of solution from between the diaphragms and adjustment of liquid levels in the other compartments by the addition of water, At the end of 47 hours the chloride content of the solution in the intermediate compartment was found to be nil and the normality of the hydroxide solution was found to be 0.52 normal with respect t0 benzyl dimethyl octadecyl ammonium hydroxide.

Eample 2 The procedure described in Example 1 was repeated with a saturated solution of octadecyloxymethyl dimethyl benzyl ammonium chloride in place of the octadecyl dimethyl benzyl ammonium salt used above. The passage of current was continued until the liquor from the intermediate compartment was low in chlorine. The resulting solution contained octadecyloxymethyl dimethyl benzyl ammonium hydroxide, which formed a gel at a concentration of about 25%.

Example 3 The procedure of Example 1 was repeated with a solution of dodecyloxymethyl dimethyl benzyl ammonium chloride. Dodecyloxymethyl dimethyl benzyl ammonium hydroxide was obtained in solution.

Dodecyl dimethyl benzyl ammonium chloride was likewise converted electrolytically to dodecyl dimethyl benzyl ammonium hydroxide in aqueous solution.

The Quaternary ammonium hydroxides of this invention are useful as swelling agents for cellulose and 'finishing agentsA for cellulosic fabrics. They are peculiarly effective for treating regenerated cellulose. They are useful for making salts of various acids when no other means of producing such salts is known.

The capillary-active quaternary ammonium hydroxides have not heretofore been available in view of vthe fact that conventional metatheses fail to give products which can be separated with isolation of capillary-active quaternary vammonium hydroxides free from soluble or insoluble salts, which might result from attempted metathesis. Thus, the method herein described, which may-be considered one of electrodialysis, yields capillary-active quaternary ammonium hydroxides which are substantially free from nonquaternary products.

I claim: 1. A process for the preparation of a capillary-active quaternary ammonium hydroxide in an electrolytic cell having an anode inert to oxygen and halogens set ofby a porous refractory diaphragm to form a compartmentv about the anode, having a cathode set oil by a second porous refractory diaphragm to form a compartment about the cathode, and having an intermediate compartment between said anode and cathode, the porosity of said diaphragms permitting the ow therethrough of about 0.001 cc. to about 0.015 cc. of water at 20 C. per square centimeter per hour under a 20 cm. head, which comprises placing about the anode of the cell an aqueous solution of a .strong acid, placing about the cathode of the cell an'aqueous solution of an alkali yielding hydroxyl ions, placing in a compartment of the cell intermediate to the anode and cathode thereof an aqueous solution of a quaternary ammonium compound having saltforming anions and having its N-substituents selected from at least one member of the class consisting of aliphatic and arylaliphatic groups, at least one of which substituents contains at least carbon atoms, and passing a unidirectional electric current through said cell until the salt-forming anions of the quaternary ammonium compound have been substantially replaced with hydroxyl ions.

2. A process for the preparation of a capillary-active quaternary ammonium hydroxide in an electrolytic cell having an anode inert to halogens set off by a porous refractory diaphragm to form a compartment about the anode, having a cathode set off by a second porous re fractory diaphragm to form a compartment about the cathode, and having a compartment intermediate to said anode and cathode, the porosity of said diaphragms permitting the ow therethrough of about 0.001 cc. to about 0.015 cc. of water at 20 C. per square centimeter per hour under a 20 cm. head, which comprises placing about the-anode of the cell an aqueous solution of a halogen acid, placing about the cathode of the cell an aqueous solution of an alkali yielding hydroxyl ions, placing in the compartment.

of the cell intermediate to the anode and cathode thereof an aqueous solution of a capillary-active quaternary ammonium halide, the N-substituents of which are selected from at least one member of the class consisting of aliphatic and arylaliphatic groups, and passing a unidirectional electric current through said cell until the halogen of the quaternary ammonium halide has been substantally replaced with hydroxyl ions.

3. A process for the preparation of a capillary-active quaternary ammonium hydroxide in an electrolytic cell having an anode inert to halogens set off by a porous refractory diaphragm to form a compartment about the anode, having a cathode set off by a second porous refractory diaphragm to form a compartment about the cathode, and having a compartment intermediate to said anode and cathode, the porosity. of said diaphragms permitting the flow therethrough of about 0.001 cc. to about 0.15 cc. of water at 20 C. per square centimeter per hour under a 20 cm. head, which comprises placing about theanode of the cell an aqueous solution of a halogen acid, placing about the cathode of the cell an aqueous solution of v an-alkali yielding hydroxyl ions, placing in the compartment of the cell vintermediate to the anode and cathode thereof an aqueous solutionv of a rvquaternary ammonium halide, the N-substit'uents of which are selected from at least one 'member of the group consisting of aliphatic and arylaliphatic groups and one N-substituent beingan aliphatic group hav-ing 12 to 18 carbon atoms, and passing a unidirectional current through said'cell until halogen is essentially removed from the intermediate compartment.

4. A process for the preparation of a capillary-active quaternary ammonium hydroxide in an electrolytic cell having an anode inert to halogens set off by a porous refractory diaphragm to form a compartment about the anode, having a cathode set off by a second porous refractory diaphragm to form a compartment about the cathode, and having a compartment intermediate to said anode and cathode, the porosity of said .diaphragms permitting the ow therethrough of about 0.001 cc. to about 0.015.,.cc. of water at 20 C. per square centimeter per hour under a 20 cm. head, which comprises placing about the anode of the cell an aqueous solution of a halogen acid, placing about the cathode of the cell an aqueous solution of an alkali yielding lhydroxyl ions, placing in the compartment of the cell intermediate to the anode and cathode thereof an aqueous solution of a quaternary ammonium chloride, the N-substituents of which are selected from at least one member of the group consisting of aliphatic and arylaliphatlc groups and one N-substituent being an aliphatic group having 12 to 18 carbon atoms, and passing a unidirectional lcurrent through said cell until chlorine is essentially removed from the intermediate compartment.

5. A process for the preparation of benzyl dimethyl octadecyl ammonium hydroxide in an electrolytic cell having an anode inert to chlorine set olf by a porous refractory diaphragm to form a compartment about the anode, having a cathode set off by a second porous refractory diaphragm to form a compartment about the cathode, and having a. compartment intermediate to said anode and cathode, the porosity of said diaphragms permitting the flow therethrough of about 0.001 cc. to about 0.015 cc. of Water at 20 C. per square centimeter per hour` under a 20 cm. head, which comprises placing an aqueous solution of hydrochloric acid about the anode of the cell, placing about the cathode of the cell an aqueous solution of an alkali yielding hydroxyl ions, placing in the compartment of the cell intermediate to the anode and cathode thereof an aqueous solution of benzyl dimethyl octadecyl ammonium chloride and passing a unidirectional electric current'l through said cell until the chlorine ions have been substantially removed from the intermediate compartment.

6. A process for the preparation of benzyl dimethyl octadecyloxymethyl ammonium hydroxide in an electrolytic cell having an anode inert to chlorine set off by a. porous refractory diaphragm to forma compartment about the anode, having a cathode set oi by a second porous refractory diaphragm to form a compartment about the cathode, and having a compartment intermediate to`said anode and cathode, the porosity of said diaphragms permitting the flow therethrough of about 0.001 cc.to about 0.015 cc. of water at 20 C. per square centimeter per hour under a 20 cm. head, which comprises placing an aqueous solution of hydrochloric acid about the anode of the cell, placing about the cathode of the cell an aqueous solution of an alkali yielding hydroxyl ions, placing in the compartment of the cell intermediate to the anode and cathode thereof an aqueous solution of benzyl dimethyl octadecyloxymethyl ammonium chloride and passing a unidirectional electric current through said cell until the chlorine ions have been substantially removed from the intermediate compartment.

f7. A. process for the preparation of benzyl dimethyl dodecyl ammonium hydroxide in an electrolytic cell having an anode inert to chlorine set oi by a porous refractory diaphragm to form a compartment about the anode, having a cathode set oil by a second .porous refractory diaphragm to form a compartment about the cathode, and having a compartment intermediate to said anode and cathode, the porosity of said diaphragms permitting the flow therethrough of about 0.001 cc. to about 0.015 cc. of water at 20 C. per square centimeter per hour under a 20 cm. head, which comprises placing an aqueous solution of hydrochloric acid about the anode of the cell, placing about the cathode of the cell an aqueous solution of an alkali yielding hydroxyl ions, placing in the compartment of the cell intermediate to the anode and cathode thereof an aqueous solution of benzyl dimethyl dodecyl ammonium chloride and pasisng' a unidirectional electric current through said cell until the chlorine ions have been substantially removed from the intermediate compartment.

LOUIS H. BOCK. 

